Electronic mail (e-mail) is a popular way to communicate with others. Electronic mail systems operate to send messages over a network. The network can include internal networks and external (e.g., public) networks. An example of an internal network is a local area network (LAN), and an example of an external network is the Internet. Typically, the electronic mail systems are LAN wide systems that reside on an internal network but also permit coupling with an external network so that messages can be exchanged with other electronic mail systems.
Recently, Internet-based electronic mail systems have been developed and implemented to provide electronic mail services over the Internet. In such systems, there may not be internal network because the electronic mail system resides on the Internet. The electronic mail system has a mail server that interacts with users' network browsers so that users are able to request electronic mail services which are performed by the mail server. Typically, the mail server is a Hyper Text Transfer Protocol (HTTP) server.
The electronic mail systems have been implemented over wired networks as well as over wireless networks. The availability of the network determines whether a client application (e.g., network browser) is in communication with the mail server. The client application operates on a local machine, whereas the mail server operates on a remote machine. In the case of wired networks, the local machine is, for example, a desktop computer. In the case of wireless networks, the local machine is a mobile device. For example, the mobile device can be a mobile telephone, a personal digital assistant (PDA) or a portable computer that has wireless local area network access to the mail server.
Because of the dependency of the operation of client applications on the bandwidth of networks, client applications often have to wait for resources from mail servers. These wait times are unacceptably long when the network is loaded. Even when the network is not congested, the client applications conventionally require substantial amounts of network bandwidth to provide the e-mail services and this tends to burden the network and induce wait times faced by users.
A cache memory may be helpful in reducing the dependency of the computers or mobile devices on network bandwidth. However, the cache memory is only helpful when the newly requested resource happens to reside in the cache memory. Still further, the cache memory is limited and cannot serve as a storage to store all the resources likely to be again requested. Moreover, mobile devices (particularly hand-held mobile devices) need to keep cache memories relatively small due to power, cost and space limitations.
Mobile devices when used as a mail terminal have further problems. An interface limitation poses significant difficulties to mobile electronic mail technology. A size of the screen of the mobile device is tiny and very limited. Mobile device's screen can only show a limited amount of information, for example 5 rows each row with 10 characters. The screen supports scarce amount of graphics. Typically, the screen can only present simple pixel graphics. Moreover, the limited bandwidth of the mobile communication poses difficulties to mobile e-mail services. For example, conventional mobile communication systems provide text messages of limited length, and result in truncation. Concatenation of messages yields back to the problem of limited size. Even the most sophisticated mobile communication system can only provide data transfer rate which is about few hundred kbits/s, and the future mobile communication systems promise about a couple hundred kbit/s more data transfer speed. Yet, e-mail messages may constitute as large as megabyte files entirely. Thus, the limited number of messages that can be shown without too great a time lag and effort cause problems when gaining mail via a mobile device. In addition, the problems limit the mushrooming of the e-mail services. For example, a rather common solution has been avoiding using the mobile device for mail purposes, or using it when other mediums have not been available.
In view of various inherent limitations of mobile devices, it would be desirable to avoid these and other problems associated with prior art systems. Thus, there is a need for techniques to provide smooth facing with information by a user seeking to utilize electronic mail service provided by a mail server across a network.